Unilateral Pyramidotomy of the Corticospinal Tract in Rats for Assessment of Neuroplasticity-inducing Therapies

The aim of this procedure is to perform a unilateral taxotomy of the cortico spinal tract in the medullary pyramids in rats in order to assess neuroplasticity after injury, whether spontaneous or induced by therapies. This is accomplished by first dissecting the neck from a ventral approach past the trachea. Next, the pyramids are exposed by craniotomy, and a lesion is made to the pyramid on one side of the base basala artery.

After the surgery, the effects of pyramid otomy can be assessed using behavioral testing, electrophysiological testing, and histology. Unilateral taxotomy of the corticospinal tracts in the medullary pyramids of adult rats causes a long-lasting deficit in dexterity. This model can be used to evaluate candidate therapies for CNS injury.

First, determine the dominant fore power of the animal using the cylinder rearing test plan to injure the corresponding pyramid. For example, sever the right pyramid rostral to the decussation to disable the rat's left hand side. After inducing anesthesia of a female lister, hooded rat with 5%is of fluorine, shave the ventral side of its neck, regulate and sustain the anesthesia.

Using around 1.5%is of fluorine. Then administer carprofen subcutaneously to reduce inflammation and provide analgesia using a homeo themic system. Maintain the animal at 37 degrees Celsius during the surgery.

Before starting, check the pinch withdrawal reflex and the blink reflex. Apply ointment to the eyes. Disinfect the exposed skin with 1%chlorhexidine in alcohol.

To begin the surgery, make a two to three centimeter midline incision, starting just cordal to the chin and ending just roral to the sternum. Then use small bulldog clamps to retract the skin blunt. Dissect the upper layers of tissue to expose the trachea.

Stay on the midline and use reverse action with blunted scissors and tooth forceps. Once exposed, displace the trachea to one side. Two white fat pads beneath.

Mark the cord end of the Bai occipital bone. Now roral to the pads blunt dissect to the ventral surface of the skull. To expose the skull, displace the trachea by at most one centimeter.

With a pair of long tooth retractors or with hook retractors, too much displacement will obstruct breathing. It may help to close the retractors for a few minutes whenever there are any signs that the rat requires better ventilation. Now, carefully cauterize the small vessels at the rostral end of the trachea towards the larynx.

Adjust the microscope and focus in on the skull. Prepare for drilling by removing the periosteum with fine forceps and adjusting the retractors To better expose the skull, probe the uneven surface of the basal occipital bone radially. There is an elevation at the midline that covers the basilar artery.

Drill a hole one millimeter lateral to the midline on the chosen side. Gradually enlarge the hole towards the midline using small vertical up and down movements. Then the basilar artery and the pyramid with its slightly bulging shape can be identified.

Any remaining bone fragments should be removed with forceps. The pyramid can then be identified by its slightly bulging shape and the bordering blood vessels apply one drop of respiratory stimulant Dora hydrochloride to the tongue to expose the pyramid. First, open the dura with a 26 gauge needle and fine forceps.

Soak up cerebral spinal fluid and blood with cotton buds. Have a pair of Venus spring scissors marked at 0.5 millimeters from the tips. Using these scissors, make a cut in the pyramid about 1.5 millimeters wide, spanning the pyramid and 0.5 millimeters deep perpendicular to the basilar artery.

This interrupts the CST fibers. After zomy, the animal might stop breathing temporarily. A short cycle of artificial ventilation using a 10 mil syringe placed over the rat's nose and mouth may facilitate recovery To ensure that the lesion includes fibers close to the basilar artery.

Retrace the cut using the tip of a 26 gauge needle. Stop the bleeding with light pressure from cotton buds. The cut can also be covered with gel foam.

Now remove the retractors and bulldog clamps and replace the tissues. Suture only the skin using three zero Vicryl sutures. Then subcutaneously.

Administer five milliliters of saline for rehydration. After the surgery, transfer the animal to a 32 degrees Celsius incubator until it is fully awake. Monitor the animal continually give daily subcutaneous carprofen injections over the next two days to control inflammation and manage pain.

Also closely observe the animal for the week thereafter. Weighing daily and giving additional fluids as required. Water bottles should have long spouts lacking ball bearing valves, weight loss of up to 20%may occur.

So place hydrogel packs in the cage together with wet mash, soft fruits, and pured baby food, hand feeding by syringe. If necessary, damage to other brainstem areas may cause barrel rolling or may cause an eyelid to remain open or closed. In some cases, animals may need to be humanely sacrificed.

Several tests were used to measure deficits due to the pyramid otomy in the cylinder rearing. Test injuries affecting the dominant fopo reduced preference significantly with gradual recovery after the lesion. The Montoya staircase test shows that the number of retrieved pellets on the contral affected side decrease significantly throughout the testing period.

Whereas ipsilateral less affected front pore behavior recovered after a week on the horizontal ladder test post-injury, the frequency of missteps increased significantly on the contral lesional affected side compared to an immediate deficit with recovery on the ipsilateral less affected side. 10 weeks post-surgery, histological analysis was performed. The uninjured corticospinal tract of the animals was traced with biotinylated dextran amine.

By injecting it into the contral lesional cortex, the dorson medial ventra medial and dos lateral components of the CST were clearly visible. Under closer magnification, fibers could be seen that extend over the midline into the gray matter of the d ated side. For example, at 10 weeks post-surgery, lesion completeness was confirmed with a transverse section at cervical level and immunohistochemistry against PKC gamma as expected one cortico spinal tract was missing.

Once mastered, the surgery can be done in 30 minutes with a low mortality rate.